1. Field of the Invention
The present invention relates to a process for the production of valerolactone.
2. Description of Related Art
Gamma-valerolactone (5-methylbutyrolactone, in the context of the invention also referred to as “valerolactone”) is a valuable compound which is inter alia used in the production of adipic acid (1,6-hexanedioic acid) which is an important precursor for inter alia the production of polyamides such as polyamide 6,6 (also referred to as “Nylon”) or polyamide 4,6 (also referred to as “Stanyl”). Further, esters of adipic acid may be used in plasticisers, lubricants, solvents and in a variety of polyurethane resins. Other uses of adipic acid are as food acidulants, applications in adhesives, insecticides, tanning and dyeing.
The most important process to produce adipic acid is based on oil and starts from benzene. A disadvantage of this process is that it is based on fossil derived oil and is therefore not renewable. Another disadvantage is the evolution of NOx during the oxidation step, which either is vented to the air, which is highly undesirable as it is a greenhouse gas, or its catalytically destroyed, which is an expensive process.
New processes for the production of adipic acid have been developed based on butadiene. However, such processes are also environmentally unfavourable.
A third production route to produce adipic acid involves the use of valerolactone which can be converted to methylpentenoates in the presence of an acidic or basic catalyst in the gas phase or in the liquid phase. Methylpentenoate can be converted to dimethyladipate in an alkoxycarbonylation reaction which dimethyladipate can be converted to adipic acid in a simple hydrolysis reaction. The use of valerolactone in the production of adipic acid is environmentally advantageous since it can be produced from levulinic acid, which in turn can be produced from renewable sources such as plant waste.
US2003/0055270 discloses a process to produce valerolactone from levulinic acid using a solid Ru catalyst, e.g. supported on carbon. A problem of the process as described by US2003/0055270 is that the selectivity towards valerolactone is insufficient. Another problem of process as described by US2003/0055270 is that the conversion yield is insufficient. The use of valerolactone in the production of adipic acid is environmentally advantageous since it can be produced from levulinic acid, which in turn can be produced from renewable sources such as plant waste.